The expansion pattern
of the three reaction zones, including oxidation,
reduction, and dry distillation zones in the underground coal gasification
(UCG) process, is recognized to be different using various gas-injection
patterns, on account of which the corresponding stability and syngas
components are notably distinguished. The current work carried out
UCG model tests in a removable gas-injection point (receded five times).
During the stable gasification process, the temperature field map
and changes in syngas composition were monitored to determine the
area proportions among the three zones and their expansion rates.
The differences in the expansion of the three zones between fixed
and removable gas-injection points were then explained according to
cavity growth. The results showed that the UCG process using a removable
gas-injection point exhibited a better performance than that using
a fixed point in some aspects, including gasification stability, syngas
calorific value, area ratio of the reduction zone and oxygen diffusion
velocity, etc., as follows. In the RGIP process, especially in the
second retraction stage, the gasification was the most stable, and
the syngas calorific value achieved the highest (7.83 MJ/m3). Meanwhile, the area ratio of the oxidation, reduction, and dry
distillation zones was 1.00:1.58:1.00, and the corresponding expansion
rates in forward and lateral directions were 0.074 and 0.008 m/h,
respectively. Compared to gasification using a fixed point, removable
gas-injection point method has led to cavity formation in each retraction
stage, which can increase the oxygen diffusion velocity. It can thereby
realize not only a stable gasification process but also a high thermal
efficiency for the energetic reaction. In addition, that stable process
can be lengthened by controlling the removable device. This explained
why the expansion of the three zones using a removable gas-injection
point was better mainly in gasification stability, efficiency, and
syngas calorific value than that using a fixed one.
This research focused on the feasibility of applying the forward and reverse combustion approach to the in situ gasification of lignite with the production of hydrogen-rich syngas (H 2 and CO). The so-called forward combustion gasification (FCG) and reverse combustion gasification (RCG) approach in which oxygen and steam are simultaneously fed to the simulated system of underground coal gasification (UCG) was studied. A simulated system of UCG was designed and established. The underground conditions of the coal seam and strata were simulated in the system. The combustion gasification of lignite has been carried out experimentally for almost 6.5 days. The average effective content (H 2 ? CO) of syngas during the FCG phase was 62.31 % and the maximum content was 70.92 %. For the RCG phase the corresponding figures are 61.33 % and 67.91 %. Thus, the feasibility of using RCG way for UCG has been demonstrated. The temperature profiles have been provided by using of 85 thermocouples during the model experiment, which portrayed the several nephograms of thermal data in the gasifier were of significance for the prospective gasification processes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.